This invention pertains to the art of the removal of nitrogen oxides (NOX) and sulfur oxides from fluid stream emissions such as those which originate from fossil fuel powered plants, flue gas, gas turbines and the like, and more particularly to the electrochemical removal of these oxides from such streams. This invention is particularly applicable to the removal of NOX and SO.sub.2 using a fuel cell type device, and will be described with particular reference thereto. It will be appreciated, however, that the invention has broader applications such as its ability to generate nitric acid, sulfuric acid, and hydrogen peroxide, and may be advantageously employed in other environments and applications.
There exists a pressing need for the development of new technologies to eliminate NOX, SO.sub.2, and other common pollutants from the atmosphere to help prevent further damage to the environment and to diminish the greater incidence of respiratory and other diseases in humans. Previous efforts in eliminating these pollutants have been made, and many of these efforts focused on the development of technologies capable of removing such pollutants by chemical means, such as conventional flue gas desulfurization, and/or electrochemical means using either porous or non-porous solid electrolytes.
In the case of NOX and SO.sub.2 removal, most electrochemical processes developed to date call for high temperature electrochemical reduction of the gas to accomplish this goal. Although some of the prior methodologies have met with some success, the development of advanced technologies for the removal of polluting gases capable of meeting technical, economic and reliability requirements may be regarded as of utmost importance. This has become of particular interest in view of the stringent standards imposed by the regulatory agencies regarding the release of gaseous and other pollutants into the environment.
While some of the electrochemical methods so far proposed may approach the desired standards with respect to the percentage of NOX and SO.sub.2 that is actually removed, the overall feasibility of the proposed processes in terms of long term performance and other considerations, such as the effects induced by the presence of impurities such as dioxygen in the effluent gas, still remains to be demonstrated.
The present invention contemplates a new and improved method for the simultaneous removal of nitrogen oxides (NOX) and sulfur oxides in a simple process configuration at room temperature. The process is not adversely affected by contaminants such as dioxygen present in the effluent gas at concentrations as high as 4%. It generates useful byproducts, and has a potential to significantly reduce emission control costs.